CH 320M/328M
Functional Groups
A functional group is a defined grouping of atoms in an organic molecule. A given functional group exhibits a
characteristic set of chemical properties, which are largely independent of the rest of the structure of the molecule in
which it is found. As a consequence, an understanding of the chemical behavior of the functional groups allows one
to predict the reactivity of a wide variety of organic molecules.
We will encounter numerous functional groups throughout our study of organic chemistry. A few of the more
important ones are listed in the table below (continued on the next page). At this stage, it is most important for you to
learn to recognize the general structures associated with these functional groups. In each case, a simple example is
provided as an illustration. (Note: A line indicates a single bond to carbon or hydrogen.)
Functional Group –
General Structure
Example
C
CH3CH3
C OH
Alkane
Ethane
Alcohol
Ethanol
C C
CH2=CH2
C O C
CH3OCH2CH3
Alkene
Ethylene
Ether
Ethyl methyl ether
C C
H C C H
Alkyne
Acetylene
Aromatic Ring
(Arene)
Functional Group –
General Structure
C SH
Example
CH3CH2OH
CH3CH2SH
Thiol
Ethanethiol
C S C
CH3SCH3
Benzene
Sulfide
Dimethyl sulfide
CH3CH2Br
C N
CH3CH2NH2
Ethyl bromide
Amine
Ethylamine
C X
(X = F, Cl, Br, I)
Alkyl Halide
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Functional Group –
General Structure
Example
O
C
O
C
O
C
H
Aldehyde
H3C
O
C
C
Ketone
H3C
O
C
Carboxylic acid
Acid chloride
OCH2CH3
Ethyl acetate
O
C
Acetic acid
Amide
O
C
CH3
O
C
O
C
N
H3C
O
H 3C
Ester
O
C
Acetic anhydride
C
O
OH
H3C
O
C
Cl
Acid anhydride
CH3
O
C
OH
O
C
H 3C
O
O
C
Acetone
Example
O
C
H
Acetaldehyde
O
C
Functional Group –
General Structure
C C N
H 3C
NH2
Acetamide
H3C C N
Cl
Acetyl chloride
Nitrile
Acetonitrile
Since the ability to recognize these functional groups, particularly when they are
incorporated into a larger, more complicated molecule, is so important, you should learn
the names and general structures of all of the functional groups on this handout as soon
as possible.